Milla Rautio and Atte Korhola
Limnol. Oceanogr., 47(1), 2002, 295–299
The distribution of the planktonic crustacean Daphnia and the occurrence of ultraviolet (UV)-protective melanin pigmentation in its body wall were studied in relation to the UV transparency in subarctic ponds and lakes in Finnish Lapland. In shallow ponds, Daphnia only occurred in those with sufficient amounts of UV-screening dissolved organic matter. The highest pigment concentration was found in these Daphnia and in populations that occurred in lakes with low organic carbon content (<2 mg L-1). Pigment synthesis was extremely low during the long winter and peaked immediately after the ice break-up at the time of the maximum underwater UV intensity. We propose that the predicted increase in UV irradiance from ozone depletion in the Northern Hemisphere spring, along with the earlier ice break-up associated with Arctic warming may favor the survival of those organisms with the ability to produce UV photoprotective pigments.